Radiotelephones generally refer to communications terminals which provide a wireless communications link to one or more other communications terminals. Radiotelephones may be used in a variety of different applications, including cellular telephone, land-mobile (e.g., police and fire departments), and satellite communications systems.
Handheld radiotelephones (e.g., cellular telephones), may have an appendage, such as a flip cover, pivotally mounted to the housing thereof that is movable between closed and open positions. A flip cover for a radiotelephone may contain a microphone, speaker, antenna or other electronic components. To facilitate one-handed operation, some radiotelephones utilize a spring-activated flip cover that is held in a closed position by a mechanical latching mechanism.
FIG. 1 illustrates a radiotelephone 10 with a "top-hinged" flip cover 12. The illustrated radiotelephone 10 includes a top handset housing 14 and a bottom handset housing 16 connected thereto to form a cavity therein. Top and bottom handset housings 14 and 16 house a keypad 18 including a plurality of keys 20, a display 22, and electronic components (not shown) that enable the radiotelephone 10 to transmit and receive telecommunications signals. A flip cover 12 is hinged to the top end 14a of the top housing 14, and is configured to house a speaker 26. An antenna 28 extends from the radiotelephone 10 as illustrated.
In operation, the flip cover 12 may be pivoted by a user about an axis A between an open position and a closed position. When in a closed position, the flip cover 12 may provide protection to the keypad 18 from unintentional activation or exposure to the elements. When in an open position, the speaker 26 within the flip cover 12 may be favorably positioned to provide audio output to a user.
Conventionally, a radiotelephone antenna is electrically connected to radio frequency circuitry (i.e., a transceiver) located within the radiotelephone housing. The antenna and the radio frequency circuitry are typically interconnected such that the impedance of the antenna and the impedance of the radio frequency circuitry are substantially matched.
Radiotelephones and other electronic devices are undergoing miniaturization. Indeed, many of the contemporary radiotelephone models are less than 11-12 centimeters in length. For aesthetic reasons, it may be desirable to eliminate antennas that extend outwardly from radiotelephones. Unfortunately, antennas incorporated entirely within a radiotelephone may not be able to achieve adequate radiation performance.
A radiotelephone antenna may be incorporated within a flip cover. Unfortunately, matching the impedance of an antenna housed within a flip cover of a radiotelephone may be difficult because the antenna impedance may be dependent on the position of the flip cover with respect to both the housing of the radiotelephone and the printed circuit board which contains the radio frequency circuitry. As these respective positions change as a flip cover is moved between stored and operating positions, an antenna conventionally exhibits at least two different impedance states, both of which should be matched to the impedance of the feed from the printed circuit board.
Accordingly, with a radiotelephone flip cover incorporating an antenna, it is generally desirable to provide an impedance matching system that can provide an acceptable impedance match between the antenna and the radio frequency circuitry, both when the flip cover is in a stored position, and when the flip cover is in an operating position. Unfortunately, incorporating impedance matching components and/or circuitry within a radiotelephone may be somewhat expensive. Furthermore, available space within radiotelephones may be somewhat limited.